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THE PESPAfiATION OF THIN FILMS OF InSb 
ON GKTSTALLINE SUBSTRATES 



ALLEN BEHLB 
B. S., Park College, 1959 

A MAbTER»S THESIS 
suhmitted in partial fulfillment of the 

\ 

requirements for the degree 

MASTER OF SCIENCE 

department of Pl^aics 

KANSAS STATE UNIVEESTTI 
Manhattan, Kansas 

1962 

Approyed byj 




up 

ii 

^^"0- TABLE OF COKTaiTS 

Page 

INTBDDUCTION , 

E3JIPM;irT .\ND PftOCJEDUHE g 

KESULTS AND CONCLUSIONS 2i 

DISCUSSION 32 

REaFEROJCES 

ACKNOU'LKDCaifJIT , 



IHTRQDDCTIOH 



Studies of the properties of thin films of indium entimonide have been 
performed using polycrystaUlne films. (3), (6). The interpretation of 
experimental data from such polycrystaUlne films is complicated by effects 
which are due to structural monuniformity. It would therefore be of value 
to be able to study monocrystalline films. The ultimate goal of the work 
described in this paper was the production of monocrystalline films of InSb 
suitable for further studies of the properties of thin films, 

A promising and widely \ised method for preparing monocrystalline filmg 
is epitaxial growth. This method is based on the fact that films deposited 
from the vapor phase onto suitable crystalline substrates often are composed 
of large oriented crystallites. 

The phenomenon of one crystal grown upon another with some definite 
and unique orientation relationship between their 'crystal axes was first 
observed in the form of natural growths among minerals. The term epitaxy 
denotes this phenomenon. Many naturally occurring cases of oriented inter- 
growth have been observed and comprehensive lists of the known examples have 
been compiled, (7). 

Observation of these intergrowths led to attempts to obtain oriented 
intergrowths in laboratory experiments. The parallel growth of sodium 
nitrate frcm solution <m the surface of a calcite crystal by Frankenhelm 
in 1836, appears to have been the first successful attempt. The first 
systematic experiments were performed by Barker who sttdied the growth from 
solution of crystals with related structures, such as the alkali halideil^ 
upon each other. He found that some alkali halides oriented upon each othw 
while others did not, and concluded that oriented growth is more likely to ' 



2 



occur if the molecular volumes of the two alkaU halides are nearly equal. (2). 

After the discovery and development of x-ray diffraction and the conse- 
quent tramendous increase in knowledge of crystal structure, fioyer repeated 
and extended the work done by Barker, On the basis of his results he devel- 
oped a theoiy of epitaxy. This theory centered on the necessity of a paral- 
lelism of the lattices accompanied by a aaall misfit value for the lattices, 
(7). 

Electron diffraction was discovered about the time Jbyer was doing his 
work. The application of electron diffraction to the study of epitaxy 
greatly increased the possibilities for study, making it possible to study 
much thinner growths and deposits other than those grown from solution. 
With the application of electron diffraction to work on various types of 
deposits, it was found that epitaxy occurs in such varied deposits as chem- 
ically gxx>\m layers, electrodepo sited metal films, and metal layers condensed 
from the vapor phase. Van der Merwe compiled a comprehensive summary of 
known cases of epitaxy and Paahley has compiled a detailed survey of those 
cases which have been studied using electron diffraction techniques. (7), (12), 

The investigation of epitaxy of metals upon non-metals has been carried 
out almost exclusively by electron diffraction. Lassen's discovexy of silver 
in parallel orientation when deposited from the vapor phase on a rocksalt 
cleavage face was the first known occurrence of this type. (7), 

Lassen and Bruck reported the growth of good, single ciystal, thin 
films of silver by deposition on heated rocksalt substrates. They reported 
the films grew in parallel orientation, which corresponds to a misfit value 
of -ZTi. itoyer challenged this observation on the basis that other possible 
orientations would result in much aaaller misfits and would therefore be the 
ones expected to occur. Lassen and Bruck, while agreeing one might expect 



3 



other orientations on the basis of misfit, confirmed that it was neverthe- 
less the parallel orientation which occurred, (9), 

Bruck and Rudiger, in their independent studies of metals deposited on 
rocksalt, fluor, and caloite, found that orientation of the films was markedly 
dependent on the substrate temperature during deposition, i'hen the deposi- 
tion was made onto substrates held at temperatures above a certain critical 
temperature (the epitaxial temperature) well oriented films were obtained. 
For depositions made on substrates at temperntures below the epitaxial tem- 
perature there was not complete orientation, ^he epitaxial temperature was 
found to be different for different metals, (2), (7), 

aiirari. carried out many experiments with metals on non-metals and 
found that in some cases where the substrates were preheated to several 
hundred degrees Centigrade and then cooled to some lower temperature for 
the deposition there was an improvement in the degree of orientation achieved, 
(7). 

Oriented growths of metals upon mica, calcite, fluorspar, and mineral 
sulphides have been studied extensively. These are characterized, in general, 
by the occurrence of mixtures of orientations which are temperature dependent. 
The misfits found in these films are often voiy high, (7). 

More recently, Kehoe examined the growth process of silver films by 
continuously monitoring the diffraction patterns from films being deposited 
in the diffraction camera. He found that good orientation occurred at temper- 
atures appreciably below previously reported epitaxial temperatures, Kehoe, 
however, used much slower rates of deposition than had been used previously. 
(5). 

Sloope and Tiller, working primarily with silver on rocksalt, were the 
first to perform ^stematic experliaents to establish some of the iaportant 



factors for the production of good single crystal thin films by epitaxial 
growth. They found the most perfect films, structurally, were produced on 
substrates that were given a preliminary heat treatment to reduce the amount 
of absorbed gao and other foreigj^ matter on the surface, 4iort periods of 
preheating were found to bo as effective as extended periods. It was also 
noted that if the substrates were preheated to temperatures where thermaJ. 
etching took place the resultant films were porous. In studying the relation 
between the substrate temperature and deposition rate they found that there 
is actually no epitaxial temperature, but that the required substrate temper^ 
ature varies with the rate of deposition, (10), * 

Kalinkin, Alesicovskii, oergeeva, and ^itraknow hava obtained monociystal- 
line films of CdSe on surfaces of NaCl, KOI, and KBr, On the basis of their 
studies they concluded that the orientation of the films did not depend to 
any significant degree on the surface relief of the substrate and that in 
obtaining monociyatalline films the most important parameters were the 
substrate temperature during deposition and the rate of deposition. They 
also observed that a preliminary heating of the cxystal substre\te increased 
the ability of the substrate to cause orientation of the film, (A). 

Extensive studies have been made of Uie occxirrence of and conditions 
for epitaxy, but there still does not exist a good theory of epitaxy to provide 
guideposts for work with previously untried materials. 

There have been many theoretical considerations of epitaxy but the 
majority of them were based on the concept of a good georaetrical fit between 
the lattices of the substrate and the overgrowth and completely ipiled to 
explain the many large misfits and varied orientations that have bean observed. 
It now seems to be commonly agreed that a greater knowlc-dge of the process of 
nucleation and of surface forces must be obtained before any comprehensive 
theory of epitaxy can be evolved. 



5 



E.5UIPMENT AND PK)CEDUJaS 

Plate I shows the vacuum chamber arrangement used throughout this inves- 
tigation. All evaporations ¥*ere joade inside a 3 inch glass tee. The tee 
was seided to a brass flange on the throat of the pumping systen by iaeans of 
a soft rubber gasket. The pumping system used to evacuate the chajober con- 
sisted of a chain of two oil diffusion pumps and a mechanical forepurap and 
was capable of an ultimate vacuum of 10"^mm Hg, The main pumping system 
could be sealed off just ahead of the chamber and the chamber itself roughed 
down by a second mechanical pump after it had been opened to the atmosphere. 
Thus the pumps were never turned off or exposed diwctly to the air. The 
gas pressure in the chamber was measured with a Consolidated Vacuum Corpor- 
ation, Philips Gauge type FHG - 09. 

Bulk Ina> was evaporated from a molybdenum boat which was mounted on 
copper high current leads. These leads passed out of the chamber through 
a brass end-piece on the side am of the tee. The power for the boat was 
supplied by a 3 kva, U to 1, stepdown transformer regulated by means of a 
100 amp Transtat Voltage Begulator in the primaiy. 

The brass end-pieces on the top and side arm were sealed to the glasa 
by means of Teflon gaskets, the pressure being applied by bolts passing 
between opposliig aluminum flanges. The top piece supported the substrate 
holder and had the heater and thermocouple leads passing through it. The 
substrate holder held both the substrate material and a glass optical flat 
approximately 11cm above the bottom of the boat. The substrate was sand- 
wiched between the substrate hater in contact vdth the rear surface and a 
brass mask over the face. The optical flat also was covered by a brasa 
mask having a rectangular slit so that the film deposited on it had two. 



long, parallel edges. The tiiLckness meaauromenfcs were made on this film by 
an optical method employing interference by reflection of sodium light with 
a wavelength of 589OA, The fringe shifts were measured with a telescope 
equipped with a microneter head. 

The optical flat was not backed with a heater and therefore remained at 
a different temperature than was being used for the substrate during the 
depod.tion of the film. The actual thickness of the films deposited on the 
ciystalline substrntes may have been somewhat different from those measured 
on the optical flat due to re-evaporation from the heated substrate. The 
relative rate of deposition for the various films was of more interest than 
the actual thickness of the film in this study. Thi.s was calculated from 
the thickness measurement and length of time to evaporate the charge. The 
deposition rate, as measured, represents only an average rate since the actxial 
deposition rate varied somewhat throughout the deposition due to factors such 
as the reduction of the size of the charge in evaporating and temperature 
changes of the crucible. 

The substrate heater was a ceramic slab on one side of which ohromel wire 
was threaded through thin parallel cuts and cemented into plaoe with Eccooeram- 
CS ceramic bonding and sealing confound. The other side was lapped flat to 
provide thermal contact with the substrates. Power was supplied to the 
heater fi%^ a transfomer regulated by a variac. 

The substrates were freshly cleaved from bulk samples of C;aF2, KBr, LiF, 
and NaCl, The only exception to this was a thermally etched (111) surface of 
Nad which had been exposed to the air for an extended length of time, Caf^ 
was used because it cleaves easily along the (HI) plane. The (111) plans 
was thought to be the most likely to produce epitaxy since InSb has the 
zinc blende structure and if it grew on a (111) face in parallel orientation 



KiPLAHATION OF PUTE I 
CttUitajr view of vaetuia ehaober axmngemcnt* 

Subatrate heater £• Optical flat 

^8trat« F, Braaa oaak 

Bl«M wtLwk Q» Ii^ybdenum boat 

SiibstrBte holder H« Current leads 



8 




9 



the crystal lattic* would grow as alternate parallel layers of In and Sb, 
KBr was tried because it has a lattice constant nearly the same as that of 
InSb, NlaCl was tried because most of the good single crystal thin films of 
yarious metala have been grown on rocksnlt substrates. LiF was used because 
it was available in large pieces with good crystal structvire. 

After the substrate was cleaved, a copper-constantan thermocouple waa 
attached to its surface with Eccobond 58C solder and the substrate was heated 
approximately 1 hour to dry the solder. The substrate was then immediately 
mounted in the vacuim system. Prior to evaporation the substrates were 
heated in vacuo to a temperature somewhat higher (50°C to 200°C) than the 
intended substrate temperature during deposition, and were held at that tem- 
perature about 2 hours or more. The substrate was then cooled in a few 
minutes to the desired substrate temperature and evaporation was begun. The 
pressure in the chamber never rose about IC^mm Hg during deposition of the 
films. The substrates were allowed to cool slowly to room temperature imme- 
diately upon completion of the deposition. The substrate temperature was 
determined from the thermocouple otf measvired with a Rubicon potentiometer 
model No. 2700, 

anall pieces of substrate with the overgrowth of InSb were carefully 
cleaved from the rest of the substrate for study by reflection electron 
diffraction. In one situation it became necessary to examine the film by 
transmission diffraction. In several cases pieces of the substrate not 
coverwcv oj/ uhe In2b were also cleaved off for examination by electron diffrac- 
tion. The electron diffraction patterns were obtained in a RCA model EMU-2D 
electron microscope equipped with a reflection diffraction attachment. 

After examination by electron diffraction, Pt-Pd shadowed carbon surface 
replicas were made of the film surfacRS. The shadowing was done by evapor- 



10 



ating th6 t>t-Pd wire from approjdmately 15° with respect to th ^ film surface. 
The carbon was then deposited at normal incidence. The replicas were rexaoved 
in dilute nitric acid and mounted on grids for exajnination in the electron 
Mcro scope. 



11 

BESULTS AND CONCLUSIONS 

Fifteen usable InSb films were deposited on (111) cleavage faces of 
CaFg. Hiese were deposited -with the substrates at various tempera ttirea 
ratgiag txom. 25°C to 300°C amd at various rates of depositioa raaglag from 
200A/min to lOOOA/min. -Vhen examined by electron diffraction all of these 
films gave good InSb diffraction patterns, but there were significant vari- 
ations in the types of pattei-ns and in the appearance of pure In and pur« 
Sb lines in the patterns. The pertinent data for the films are compiled in 
Table 1. 

Slower deposition rates were found to be more favorable for the foma- 
tion of InSb films with larger crystallites. Films A-11 and A-3 were both 
deposited on substrates held at 200°^, but the deposition rate for film A-.3 
was double that of A-11. The diffraction pattern for film A-11 (Plate II, 
Fig. 1) shows spots and grainy rings ■whereas the diffraction pattern for 
film A-3 (Plate II, Fig. 2) shows only continuous rings. Films A-I4 and A-I5 
were also deposited on substr-tes held at the same temperature (300°G), but 
the depo^tion rate for film A-I5 was double thr.t of film A-I4. Here, as 
before, the diffraction pattern from the mre slowljr deposited film, film 
A-14 (Plate III, Fig. 1), contained well-defined spots while the pattern 
from the more rapidly deposited film, film A-I5 (Plate III, Fig. 2), con- 
tained only continuous rings. The spotted patterns from the films deposited 
with the slower deposition rates show the crystallites in these films are 
somewhat larger than those iii the corresponding films formed at faster 
deposition ra.es and having only continuous rings in their patterns. 

There was a definite darkening of segments of the rings in the diffrac- 
tion pattern from film A-4 (Plate IV, Fig. 1) deposited at a substrate 



Table 1, 


Data for InSb 


films. 12 


i3ub. 
Film Temp, 
°G 


■ Uep. 
, Rate 
A/mln 




^ Diffraction Pattern 

(d-spacings for lines present) 




1000 


InSbi 3.74,2.29,l«95,1.49,1.32j In: 1.68l ^: 3.10,1,77 
Unknown; 2,87 


A-e 100 


400 


la'dbi 


3.74,2.29,1.95,1.62,1.49,1.145; In: -^71} 3.10 

"cak spots 


A-9 125 


300 


InSbi 


2.29,1.95,1.62,1,49,1.32; Sb: 3.10} Unknown: 3.46 

Spots 


A-7 150 


200 


In 3): 


3,74,2,29,1.95,1«62,1.49,1.32,1.25,1.U5,1.09,0.935, 
0,907 '-eak spots 


A-5 150 


300 


InSb: 3.74,2. 29,1.95,l»62,l»^9,1.32,l,25,1.145,0,907j 
Sb: 3,10 Weak spots 


A-6 150 


800 


Ini:ibt 


2,29,1,95 ,1.49,1.32,1.U5 J In: 2.72,1,68,1.47 


A-1 150 


800 


InSb: 


3,74,2,29,1.95,1.49,1.32j In: 2.72,1,631 ^: 3.10,1,76 

..eak spots 


D-1 150 


200 


Inaa: 


2.29,1.95,1.145 Veiy faint pattern 


B^l 150 


700 


InSbx 


2.29,1.95,1.49,1.32,1.25,1.145 


A-ll) 175 


400 


InS): 


2,29,1.95,1.62,1.49,1.32,1.25,1.145; In: 2.72 


A-H 200 


500 


InSb: 2.29,1.95,1.62,1.49,1.32,l,25,1.145,1.02j In:272 
Sb: 3.54 %)ots 


A-3 ?00 


1000 


InSb: 


2,29,1,95,1.62,1.49 ,1.32,1.U5,1.09,0.907,0,810 


D-2 200 


400 


Inob: 


2.29,1.95,1.49,1.32,l.U5j In: 2,72,1.40j Sb: 1,76, 
1.55,1.36 


200 


300 


In^: 


2,29,1.95,1.49,1.32,1.25 


A46 225 


300 


In a): 


3,74,2.29,1.95 Trananis&ion pattern 


A-33 250 


300 


Inai: 


3.74,2.29,1.95 ,1.62,1.49,1.32,1.25 ,1.U5,1.09,1. 02, 
0,935,0,907,0.066 


A-Ii 250 


400 


InSb: 


* 

1.95,1.62,1.49,1.32,1,25,1.10,0,935,0,907 


A-14 300 


200 


InSb: 


1,95,1.62,1.32,1.25,1.145,1.09,0.935,0.866; 310 

Spots 


A-^ 300 


400 


Ina>: 


2,29,1.95,1. 2,1,49,1.32,1.25,1.U5,1.09,1.024, 
0.935,0.907,0,666 


C*2 ? 


400 


InSb: 


2,29,1,95 ,1.U5 J In: 2,72,1,685 1,55 



* A denotes CaF- substrate; G, LiF substrate; D, KBr substrafce;£, NaCl substrate 



EXPLANATION OF PLATE II 
Fig. 1, Electron diffraction pattern from film A-11, 
Fig, 2. Electron diffraction pattern from film A-3. 



PUTE II 




EXFUNATION OF PLATE in 
Pig. 1. Electron diffraction pattern from film A-U. 
Fig, 2, iilectron diffraction pattern from film A-I5, 



EXPLANATION OF PUTE IV 
Fig. 1, Electron diffraction pattern from Him A-4. 
Fig, 2. Electron diffraction pattern from film A-14. 




Fig. 2. 



19 



temperature of 25 G, This was interpreted as due to a sli^t tendency towards 
orientation of the ciystallites composing the film. For materials producing 
monociystalline films, a higher degree of orientation of the crystallites 
la found in films deposited at higher substrate temperatures. The only 
evidence for orientation of the ciystallites in InSb films deposited at sub- 
strate ten^eratures above 25°C was from film A-U, deposited at 300°C. The 
aajor spot pattern of multiple spots in the pattern from one setting of film 
A-U (Plate III, Fig. 1) suggests that several crystallites were in nearly 
the same orientation. This orientation was not characteristic of this entire 
film, however, as diffraction patterns from other areas (Plate IV, Fig. 2) 
did not show evidence of ciystallite orientation. 

In general, the best olycrystalline InSb films produced on CaF2 sub- 
strates were produced on substrates held between 200°C and 300**C during 
deposition. This is evidenced by the good In* diffraction patterns obtained 
from these films with notably fewer pure In and pure Sb lines occurilng in 
the patterns. A very excellent InSb diffraction pattern was obtained from 
film A-13 (Plate V, Fig, 1) deposited with a substrate temperature of 250°C, 
The peculiar background associated with the pattern from film A-13 v>as 
also found in the diffraction patterns of film A-? (Plate V, Fig. 2). The 
background changed in orientation with different settings of the film with 
respect to the electron beam but remained of the same general nature for 
all orientations of the samples. No reference to this phenomenon has been 
found in the literature and nothing was observed which would possibly explain 
its existence in the patterns from these films. 

All films deposited on CaF^ substrates at temperatures above 200°C were 
extremely loose on the substrates when removed from the vacuum system. In 
80IM instances the whole film or a portion of it fell off the substrate 



SXPLASATION OF fU!^^ V 
1, ELectroft diffraction pattern, from film A-13. 
fig, Zt Electron diffraction nattem from film A-8. 



22 



during subsequent handling. This looseness was attributed to the difference 
in the coefficients of expansion for the two materials. 

lii several cases good electron diffraction patterns nere obtained from 
the substrate material of the samoles before serious charging effects set in. 
These patterns, obtained from the substrate material of films A-7 (Plate VI, 
Fig. 1 and Fig. 2), k-lU (Plate 711, Fig. 1), A-l^ (Plate VII, Fig. 2), and 
A-17 (Plate VIII, Fig, l), show the substrate material had the very good 
crystal structure desired for epitaxy. This is evidenced by the good spot 
patterns and Kichuchi lines obtained from these samples. The ^mmetrioal 
elongation of the spots in the patterns is characteristic of a lack of pene- 
tration of the electron beam into the surface with a corresponding relax- 
ation of the Bragg condition. 

For a given set of conditions, GaFg seemed to foster better films of 
InSb than the other substrate materials used. Diffraction patterns were 
obtained from InSb films deposited on (100) faces of KBr and NaCl at 150**C, 
on a (100) face of KBr and a (111) face of NaCl at 200°C, and from one film 
on a (100) face of LiF p.t unknown substrate temperature. Some of these pat- 
terns were very faint. No evidence of orientation or crystallite growth was 
found in these films. A much greater separation of components, giving rise 
to pure In and pure 3b lines in the diffraction patterns, was found to exist 
in the films on KBr and LiF than in comparable films on CaF2. Good InSb pat- 
terns were obtained from the films on NaCl. 

The surface micrographs (see Plate VIII, Fig, 2, and Plate IX, Fig. 1 
and Fig, 2, for representative examples) were prepared with the idea that 
some information as to crystallite size, shape, or orientation ai^t be 
obtained but such was not the case, A correlation between the appearance of 
the film surface and its diffraction pattern was sought, but there was no 



EXPLANATION OF PLATE VI 

Fig. 1, Electron diffraction pattern from the substrate 
of film A-?. 

Fig, 2. iilectron diffraction pattern from the substrate 
of film A-7. 




Fig. 2, 



EXPUNATION OF PLATE VII 



Fig, 1, Electron diffraction pattern from the substrate 
of film A-14. 

Fig, 2, Electron diffraction pattern from the substrate 
of fiLa A-16. 



PUTE VII 



26 




Fig. 2 



EXPLANATION OF PLATE VIII 



Pig, 1, Electron diffraction pattern from ttie substrate 
of film A-17. 

Fig. 2. fiectron miscroscope laicrograph of a airfsce 
replica of film A-9. 



PLATE VIII 



28 




Fig. 1.. 




Fig. 2. 



EXPUNATION OF PLATE IX 

Fig, 1, Electron microscope micrograph of a surface 
replica of film A-4, 

Flg» 2» -.lectiKin fidci'oscope cdcrograph of a surface 
replica of film A-2. - 




Fig. 2» 



31 



recognizable difference between the surface features of films giving dif- 
fraction spots on their patterns ami those of films giving only rings. The 
fflicrographs did show that the films produced were, with one possible excep- 
tion, continuous. Much of the value of the airface micrographs was lost 
because no way was found to remove the carbon replicas from the CaF2 with- 
out serious damage to the replica and thus it could not be determined which 
structures observed on the film surfaces were due to substrate surface 
features and which were inherent with the films. 



32 



DISCUSSION 

It Has shown that slower deposition rates favor the growth of InSb films 
with larger ciystallites. The slowest rate of deposition used in this inves- 
tigation was 200A/xnin. Slower rates were not used because bulk InSb under^ 
goes component separation upon evaporation and the more volatile Sb initially 
evaporates at a much faster rate than the In, Thus, the first layers cm the 
substrate are almost pure 3b and the last layers almost pure In with vaiying 
combinations of the two components in between. The slower the evaporation 
rate the more pronounced this separation tends to become. This separation 
requires that some sort of diffusion mechanism must be operative after the 
coa^onents reach the substrate in order to produce good InSb films. The 
rebuilding of the Ina) lattice by diffusion of the componftnts is probably not 
veiy conducive to formation of extensive ciystallites in the films. Thus 
it would be of great interest to attempt epitaxial growth of InSb by use of 
the three temperature technique whereby the components are evaporated from 
separate crucibles onto a substrate held at some given tonperature, V,ith 
this method, deposition rates in the order of a few Angstroms per minute could 
be worked with and good InSb layers would be developed at all stages of 
growth rather than by some process after deposition is completed. Thus, 
films with rather large oriented cxystallites mi^t be obtained. 



33 



mFEmms 

1. Beeching, R. 

Electron diffraction. New York: Chemical Publishing, 1936. 

2. Buckley, K. ii, 

Cxystal growth. Mew York: John '/.'iley, I95I, 

3. Dale, £« B. and Senecal, G. 

Annealing effects in evaporated laSb films, J. Appl, Ftyr. 33:2526-2532, 

U, Kalinkin, I. P. et al. 

Preparation of mono crystalline layers of cadmium selenide, Soviet Plyrsics- 
SoUd aate, 3:1922-1927. 1962. 

5. Kehoe, R, B. 

On the texture of evaporated films, Phil, Mag. 2:455-566. 1957. 

6. Kurov, G. A, and Pinsker, Z, G, 

Investigation of thin films produced by evaporating indium antinionide 
in vacuum, Soviet Physic s-Technical Physics, 3:1958-1963, 1958, 

7. Pashley, D, iV, 

The study of epitaxy in thin surface films. Adv. Phy. 5:173-240. 1956. 

8. Pinaker, Z. G, 

Electron diffraction, London: Butterworths Scientific Publicationa, 
1953. 

9. Seifert, H. 

Structure and properities of solid surfaces, Chicago: University 
Chicago, 1953. 

10, Sloope, B, W, and Tiller, C. 0, 

Fomation conditions and structure of thin epitaxial silver films on 
rocksalt, J, Appl. ihy. 32:1331-1336. 1961. 

11, Thomson, G, P. and Cochrane, W, 

Theory and practice of electron diffraction, Londwi: Macmillan, 1939, 

12, van der Merwe, J, H, 

liisfitting monolayers and oriented overgrowths, Diec, Fard, Soc, 
5J201-2U. 1949. 



3A 



ACKNO??LEDCa£SNT 

I wish to thank Dr. E, B, Dale whose encouragement and assistance 
contributed so greatly to ity vjork and Dr. E« D. Dragsdorf for his valuable 
assistance. 



THE PREPAR4TI0N OF THIN FILUo OF InSb 
ON CiSSTALLINE OJBbTfl/.TiiS 



ALLi^N B 
B. S,, Park College, 1959 



AN ABailiACT OF 
A UkrJIER^S THESIS 

submitted in partial fulfillment of the 
requirements for the degree 
MASTER OF SCIENCE 
Depai^tment of Physics 

KANSAS iJTATE UNIVERSITY 
Manhattan, Kansas 

1962 



ABSTRACT 



In studies of the properties of thin films of InSb it has been found 
that the interpretation of the experimental data has been complicated by 
effects due to the polycrystalline nature of the films studied. The pur- 
pose of this noxk was to develop methods of preparing monocrjrstalline films 
of InSb suitable for further studies of the properties of thin films. The 
epitaxial growth of films by deposition from the vapor phase on crystalline 
substrates has proved highly successful for the production of monociystalline 
films of fflciny materials and thus was the method employed for this study. 

The crystalline substrates used were primarily (111) cleavage faces of 
Ca?2 but several films were also produced on (100) cleavage faces of NaCl, 
KBr and LiF and on one (HI) face of NaCl, These substrates were given a 
preliminary heat treatment In vacuum and were allovjed to cool to the desired 
Bubetrate tezapei-ature for the deposition of the film. The substrate temper- 
atures ranged from 25°C to 300°C and the depositiwa rate ranged from 200A/min 
to lOOOA/oin for deposition of the various films, Small pieces of the sub- 
strate with the InSb film were cleaved from the rest of the substrate for 
examination of the films by reflection electron diffractica. After this 
examination a Pt-Pd shadowed carbon surface replica was made of the film 
for examination in the electron microscope, 

Evidence was found that, othoz- conditions being similar, slower rates 
of deposition favor growth of larger crystallites. A sli^t orientation of 
the crystaJlites was found in the film produced on CaF2 at 25®C, The onljr 
evidence for orientation of ciystallites In films produced on substrates at 
high«r temperatures came from one arc? of a film deposited on a substrate 
held at 300°C. Study of the diffraction patterns from all of the filee 



showed that, in general, the best polycrystalline Jn3b films were obtained 
from deposition on CaF^ substrates in Uie temperature range of 200°C to 300OC. 
The fldcrographs of the carbon surface replicas showed that the films produced 
were, with one possible exception, continuous. There was a great yariation 
in the surface characteristics of the films but no correlation was found 
between the surface features and the type of diffraction patterns obtained 
from the films.